1. Field of the Invention
This invention relates to remotely activated circuit breakers, in general, and to remotely activated circuit breakers which are tripped by current sensing rather than thermal sensing, in particular.
2. Prior Art
There are many circuit breakers known in the art. Circuit breakers have many uses and, consequently, many designs. Typically, circuit breakers are used in lieu of fuses inasmuch as circuit breakers can be reset and are not permanently disabled.
One particular type of circuit breaker is a remotely activated circuit breaker. This type of circuit breaker finds application in many environments. For example, in a hostile environment, the circuit breaker may be located remotely from the activating, i.e. setting or resetting, switch.
In another application, a remotely operated circuit breaker is utilized in aeronautics systems. Thus, the circuit breaker can be located immediately adjacent to a power supply and the remote set and/or reset switch can be placed in a remote location. The remote location is, typically, the cockpit or flight deck of an aircraft, or the like. In this arrangement, the heavy duty wiring normally connected between the circuit breaker and the power source need not be utilized in the circuit from the power source (which can be in the fuselage of the aircraft, for example) to a switch in the cockpit of the aircraft. Rather, the circuit breaker is located adjacent to the power supply and a lightweight control signal wire can be connected to the remote switch in the cockpit area.
There are known remote circuit breakers of this type. However, most of these utilize thermal sensing devices to activitate the circuit breaker. In a conventional circuit breaker, a bi-metallic sensor device is heated by the current passing therethrough. The bi-metallic sensor device flexes and bends as a function of the temperature generated by the current therethrough. Ultimately, the bi-metallic sensor device trips a spring loaded mechanism to open the contacts of the circuit breaker in response to a current overload in the system. Obviously, the thermal sensor device is relatively slow acting, has a relatively wide tolerance range and the attendant questions of accuracy in operation. Moreover, the thermal sensing device exhibits a single (albeit not very precise) operating range.